Rolling mill control system



Feii. 3-, 1970 susuMu NOMURA ROLLING MILL CONTROL SYSTEM Filed Dec. 22, 1967 United States Patent 3,492,845 ROLLING MILL CONTROL SYSTEM Susumu Nomura, Yokohama-shi, Japan, assignor t0 Shibaura Kyodo Kogyo Kabushiki Kaisha, Tsurumi-ku, Yokohama-slli KanagaWa-ken, Japan, a joint-stock company of Japan Filed Dec. 22, 1967, Ser. No. 692,923 Claims priority, application Japan, Dec. 30, 1966, 41/ 85,862 int. Cl. B21b 37/02, 37/12 U.S. Cl. 72-8 2 Claims ABSTRACT OF THE DISCLOSURE In a four-high rolling mill, an electrical signal representing the rolling load, an electrical signal representing the force exerted by mill screws, and an electrical signal representing the distance between axes of working and back-up rolls are compared to control a hydraulic cylinder acting upon one of the back-up roll bearing clocks so as to maintain constant gauge.

BACKGROUND OF THE INVENTION This invention relates to rolling mill control systems and more particularly to an apparatus for eliminating effects caused by displacement of rolls of rolling mills whereby to prevent variations in the gauge of the plates or sheets due to displacement of the rolls.

It is well known in the art that displacements of back-up rolls of a rolling mill whose roll gap is maintained at a constant value by hydraulic pressure are reflected in the longitudinal gauge of the products reduced by the rolling mill so that it is difiicult to obtain products having constant gauge.

Accordingly, it is an object of this invention to provide an effective control system capable of eliminating the effeet on the gauge of the plates caused by the displacement of backup rolls or at least a portion of the effects caused by the variation in the diameter of the roll or at least a portion of the effect caused by the displacement of the axes of rotation of the back-up or working rolls due to variations in the thickness of the bearing oil film caused by the variations in the load or speed of the rolls.

In accordance with this invention, there is provided a novel control system for a rolling mill including a pair of working rolls, a pair of backup rolls, mill screws for adjusting the position of said back-up rolls, said control system comprising a hydraulic cylinder associated with one of said back-up rolls, a first load cell associated with at least one of said mill screws for generating an electrical signal representing the force exerted thereby, a second load cell associated with the other of said back-up rolls to provide an electrical signal representing the rolling load, means associated with said working and back-up rolls for generating an electrical signal represent-ing the distance between the axes of said working and back-up rolls and means to compare said electrical signals to control said hydraulic cylinder.

BRIEF DESCRIPTION OF THE DRAWING This invention can be more fully understood from the following description taken in connection with the accompanying drawing in which a single figure illustrates one embodiment of this invention, partly in schematic side elevation and partly in block diagram.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the accompanying drawing, a iiourhigh rolling mill shown therein comprises a pair of housings 16 (only one of which is shown) each including a rectangu-lar vertical window 17. A pair of work-ing rolls 1a ice and 1b and a pair of back-up rolls 2a and 2b are disposed between housings and opposite ends of these working rolls, and the back-up rolls are respectively supported by working roll bearing chocks 8a and 8b and back-up roll hearing chocks 7a and 7 b. The working roll bearing chocks are slidably received in recesses in back-up roll bear-ing chocks 7a and 7b which are slidably received in windows 17 of housings 16 in a manner well known in the art. A pair of adjusting rods 4 are secured to or urged against the upper surface of the lower back-up roll bearing chock 7b and freely pass through upper back-up roll bearing chock 7a. A load cell 3 is interposed between the upper end of each adjusting rod and screw 18 of the mill to measure force P applied to the adjusting rod. Another load cell 5 is interposed between the upper surface of the upper back-up roll bearing chock 7a and an upper yoke of the housing to measure force P or rolling load on the back-up rol-l. Devices 6a and 612, such as differential transformers, potentiometers and the like are interposed between cooperating pairs of back-up and working roll bearing chocks 7a, 8a and 7b, 8b to measure variations in the spacing therebetween to generate electrical signals representing said variations. As shown in the drawing the lower back-up roll bearing chock 7b is urged upwardly by a hydraulic cylinder 9 interposed between the bottom thereof and the bottom yoke of the housing. Electric signals from measuring devices 6a and 6b are added by an adder 10 to provide a signal representing the deviation of the sum from a reference signal. As the outputs from load cells 3 and 5 are comparatively smaller than those from measuring devices 6a and 6b, they are amplified by amplifiers 11 and 12, respectively, and the output eR fro-m amplifier 12 is further converted into a proportional output Ce by a multiplier 13. A comparator 14 which may include an amplifier is provided to compare the output signal from adder 10 with the out signals from amplifier 11 and multiplier 13 to provide an output signal to control a pressure regulator 15 for the fluid pressure supplied to the hydraulic cylinder 9.

In the above arrangement, if S; represents the roll gap, P the rolling load, S the roll gap when load P on both adjusting rods 4 is zero, K the spring constant of the roll system, and K the spring constant of adjusting rods 4, the following equation can be obtained.

PR PB KR KB (1) Further, if it is assumed that the ratio between P and P is maintained at a constant value and the l/C represents the proportional constant, then the left hand side of Equation 2 becomes zero which means that the roll gap is independent of the rolling load.

On the other hand, if

K (Ki then the left hand side of Equation 2 will have a definite value. Displacement of one or both of back-up rolls 2a and 215 causes a result equivalent to the variation in roll gap S thus causing the plate gauge to vary.

The comparator 14 functions to establish a relation By introduction into Equation 3 a quantity proportional to the sum S of two signals representing displacements of back-up rolls 2a and 2b measured by measuring devices 6a and 6b, we obtain CP P KBS When Equation 4 is substituted in Equation 1, the following equation representing the control for the operation wherein rolls are displaced can be obtained.

KB. KB

Since signal S representing roll displacement is included in both the left and right hand sides of Equation 5, it is clear than Equation is equivalent to Equation 2.

Thus the effects of roll displacements are eliminated, so that the relation between roll gap and rolling load as expressed by Equation 2 can be always maintained irrespective of the presence or absence of roll displacement.

Adder supplies an electric signal e =eK S which represents the roll deflection. Since electric signals produced by load cells 3 and 5 are substantially smaller than signals produced by measuring devices 6a and 6b, they are amplified by amplifiers 11 and 12 to a magnitude ,comparable to that of signal e Amplifier 11 provides an output signal e sP Output signal =eP representing the rolling load P is converted into a signal Ce by means of multiplier 13. Comparator 14 functions to compare these signals to obtain a signal e according to the following equations Difference signal e is applied to pressure regulator 15, which regulates the pressure of the fluid supplied to fluid pressure cylinder 9 so as to reduce signal e to zero. As the pressure regulator, an electric oil pressure type servo valve is preferred. The regulator operates to increase or decrease the fluid pressure supplied to fluid pressure cylinder 9 in response to the magnitude and polarity of signal e.

Operation of fluid pressure cylinder 9 results in variation of P and P and hence in variation of the output from comparator 14 so that the pressure of the fluid supplied to hydraulic cylinder 9 is adjusted until output signal is reduced to zero.

Thus, according to the novel control system, effects of roll displacement can be eliminated, thus providing products of uniform longitudinal thickness.

It should be understood, of course, that the foregoing disclosures relates to only a preferred embodiment of the invention and that it is intended to cover all changes and modifications of the example of the invention herein chosen for the purposes of the disclosure, which do not constitute departures from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. A control system for a rolling mill including a pair of working rolls, a pair of back-up rolls, and mill screws for adjusting the position of said back-up rolls, said control system comprising a hydraulic cylinder associated with one of said back-up rolls, a first load cell associated with at least one of said mill screws for generating an electrical signal representing the force exerted thereby, a second load cell associated with the other of said back-up rolls to provide an electrical signal representing the rolling load, means associated with said working and back-up rolls for generating an electrical signal representing the distance between the axes of said working and back-up rolls and means to compare said electrical signals to control said hydraulic cylinder.

2. The control system according to claim 1 wherein said means to compare said electrical signals comprises a comparator used to provide an output signal corresponding to the difference between said three electrical signals, and said output signal controls the pressure of the fluid supplied to said hydraulic cylinder so as to reduce said output from said comparator.

References Cited UNITED STATES PATENTS MILTON S. M'EHR, Primary Examiner US. Cl. X.R. 72-11, 16 

